The neural regulation of pituitary gonadotropin (GTH) secretion and of sexual behavior differs in the male and female rat, and these differences are established postnatally by the steroid hormone environment. The proposed work will attempt to identify the specific components of the neural substrate for the regulation of both GTH secretion and sexual behavior in the adult, and the possible site of the permanent organizing action of gonadal steroids in the neonatal rat. Particular emphasis will be placed on the delayed anovulation syndrome, and attempts made to determine the sequence of events leading to sterility, and to use the release of GTH in response to the positive feedback action of gonadal steroids as an index of hypothalamic functional state. In the adult female, sexual behavior is facilitated by the action of estrogen and progesterone apparently in the preoptic area and mesencephalic reticular formation, respectively. Electrophysiological techniques will be used in an attempt to elucidate the interaction between these two hormone dependent systems. Techniques to be employed will include the radioimmunoassay of GTH, stereotaxic surgery in the newborn and adult rat, including the intracranial implantation of hormones and drugs within specific loci, injection and surgical procedures in the fetal rat, electrochemical and electrical stimulation, the recording of the electrical activity of individual neurons, and the quantitative analysis of sexual behavior. BIBLIOGRAPHIC REFERENCES: Kubo, K., Mennin, S.P. and Gorski, R.A. (1975). Similarity of plasma LH release in androgenized and normal rats following electrochemical stimulation of the basal forebrain. Endocrinology 96: 492-500. Mennin, S.P. and Gorski, R.A. (1975). Effects of ovarian steroids on plasma LH in normal and persistent estrous adult female rats. Endocrinology 96: 486-491.